This invention relates to the art of replicating holograms or other microstructures by plastic molding, specifically where the hologram or other microstructure is formed on a surface of a utilitarian molded part.
There are many applications where it is desirable to include a hologram or other light diffractive surface relief pattern on the outside surface of a molded plastic part. An example is a bottle cap used on a consumer goods container, such as a cosmetic container and the like, that is made by an injection molding technique. The ability for a consumer to view a holographically reconstructed image or other light pattern in light reflected from a portion of the bottle cap can form a desirable portion of the overall container appearance in order to attract customers to purchase the product.
A predominant technique for forming plastic molds is by mechanically machining them in the shape of the article to be produced. It has been suggested that an insert be positioned against an inside surface of such a mold in order to form a hologram simultaneously with forming the molded piece. The insert in such a case is a thin surface relief hologram metal master. Formation of the hologram in the surface of the molded part at the same time the molded part is formed is an improvement over the two-step procedure wherein the molded part is first made in a normal manner and then a separate hologram replica in the form of a film is subsequently attached to the molded part.
It is a primary object of the present invention to provide an improved technique for mass replicating a surface relief hologram, diffraction grating, or other microstructure.
It is a more specific object of the present invention to provide an improved method of forming a surface relief hologram, diffraction grating or other microstructure on the surface of a replicated plastic part simultaneously with that part being molded.
It is also an object of the present invention to provide improved molds that include a master surface relief hologram, diffraction grating or other microstructure, and improved articles molded therefrom.